Wellbore cleanup tools typically have a mandrel with a screen around it so as to define an annular space in between for accumulation of debris collected from the wellbore. Typically, some fluid diversion device is supported from the mandrel so that in at least one direction of movement of the tool, there is flow into the annular space and through the screen leaving the debris trapped in the annular space. The flow diverter can be fixed or movable with a movable design illustrated in U.S. Pat. No. 6,607,031 where one or more cup seals are illustrated. Some diverters block the flow totally such as one or more stacked cup seals while other designs just severely impede flow around the outside of the tool when directing flow into the annular space.
Since the cleanup of well fluids with these tools principally occurs with movement in a singe direction, it is desirable to get the tool to move at maximum speed in the opposite direction where no or very little capturing of debris actually occurs. The problem occurs with diversion devices that maintain wellbore wall contact in both directions, such as cup seals. For example, if the tool is designed to direct well fluids into the annulus behind the screen when being pulled out of the hole, when the tool is run into the hole, the cup seals still resist fluid movement past them even though they are deflected from the wellbore wall. When this happens, the speed with which the tool can be run into the wellbore is reduced or a risk develops of pressurizing the formation when running in the tool. This can occur when the insertion speed displaces fluid at a faster rate than fluid can bypass the cup seals. Building pressure on the formation can reduce its productivity while slowing the tool speed creates needless expense in operating expenses for surface personnel.
What is needed is a solution that allows delivery of the tool without speed restrictions while when the movement is reversed proper diversion of debris laden fluid into the annular space between the mandrel and the screen regardless of the design of the flow diverter. Several solutions are explored to this problem that focus on simple construction that will stand up to the downhole environment. These and other aspects of the present invention will be more clear to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings with the claims spelling out the full scope of the invention.